The present invention relates to a magneto-optical recording medium having guide tracks, and more particularly to a magneto-optical recording medium having a vertically anisotropic magnetic film layer on one flat surface thereof and guide tracks on the other side opposite to the magnetic film layer.
Generally, a magneto-optical information storage apparatus capable of performing high-density recording has recording tracks with a width of about 1 .mu.m. In such a magneto-optical information storage apparatus, information recording and reproduction are performed by use of an extremely sharp thin laser beam. Therefore, it is necessary to cause the laser beam to follow accurately the necessary track for recording or reproduction, without coming into a wrong track. In order to accomplish this, an extremely accurate optical system or servo-mechanism having guide tracks is necessary.
Conventionally, the following guide track systems are known for use with a magneto-optical recording and reproduction apparatus:
(1) Guide track system in which a magnetic-film-coated recording and reproduction medium having grooved guide tracks is employed.
(2) Guide track system in which a magnetic-film-coated and reproduction medium having vertically (i.e., normal to the surface of the medium) anisotropic magnetic portions and horizontally (i.e., along the surface of the medium) magnetic portions is employed, and guide tracking is performed along the horizontally anisotropic magnetic portions.
(3) Guide track system in which a magnetic-film-coated medium having an amorphous portion and a crystalline portion is employed, and guide tracking is performed along the crystalline portion.
The first guide track system has the shortcoming that, since it is necessary to coat a magnetic film on a non-uniform surface of a medium base, it is difficult to form a magnetic film with a uniform thickness, and, accordingly, it is difficult to obtain constant magnetic characteristics necessary for the guide tracking. The only advantage of the guide track system is that the recording medium can be mass-produced.
In the case of the second guide track system, a vertically anisotropic magnetic film is coated on a flat medium base, and horizontal anisotropic guide tracks are then formed in the magnetic film by heat application using sharp laser beams. The shortcoming of this guide track system is that the mass-production of the recording medium is difficult.
In the case of the third guide track system, a vertically anisotropic amorphous magnetic film is formed on a flat medium base, and crystalline guide tracks are formed in the amorphous magnetic film by heat application using sharp laser beams. The shortcoming of this guide track system is that mass-production of the recording medium is difficult.